From the pictures I feel quite convinced that this hilt is made from hippo ivory as said by Detlef for the following reasons (not supported by any academic research but only practical experience):
. The dotted line is very characteristic of the hippo ivory and different from the age cracks of elephant ivory.
. Walrus ivory has a marble appearance if observed in cross view and this should reflect on the external visual appearance of the hilt, which is not the case.
. I have some doubts that walrus ivory was widely used for making kris hilts because it would involve trading links with Russia while it is widely accepted that the Bugis traded hippo and elephant ivory with East Africa, either directly or with the Omanis who controlled the area.
I refer you to the well-documented book from Wolfgang Schilling: "Faszination kris - Zauber des Materials" about the subject.
By the way I never observed any Schreger/ Retzius line in a piece supposedly made from hippo ivory...
Of course I remain open to discussion and am ready to change my mind if anybody can convince me otherwise
Best regards